The series of rocks on the north side of Lake Huron, to which the name Huronian was first applied, is made up largely of quartzites, but to the north and west of this region these form only a minor portion, or are altogether wanting in the bands called Huronian, and which are composed principally of the other rocks, associated with the Lake Huron quartzites. They consist of more or less massive diorites, argillaceous and dioritic slate-conglomerates, granites and syenites, schistose and jaspery iron ores, limestones or dolomites, and imperfect gneisses, together with a great variety of schists, such as mica and hydro-mica, talcoid, chloritic, dioritic, argillaceous, silicious, epidotic, hornblendic, felsitic and dolomitic. Within the general limits of the Laurentian area, nearly all the metallic ores and other useful minerals, as yet known, have been found in these rocks, and, therefore, their discovery and correct delineation on the geological map are important. As far as our explorations have gone, rocks of these kinds, and which may for convenience be styled Huronian, are much more abundant in the region between the Great Lakes and Hudson’s Bay than anywhere in the Labrador peninsula or north of Hudson’s Strait. They have been found at three places on the east coast of James’ and Hudson’s Bay. (See Report of 1877.) Mr. John McLean mentions them south of Ungava Bay. Some of the rocks of Nachvak, on the Atlantic coast, may be classified with them; and they are believed to occur at Ramah and near the entrance of Hamilton Inlet, on the same coast. GEOLOGY OF THE WEST COAST OF HUDSON’S BAY. [Sidenote: Eskimo Point to Chesterfield Inlet.] [Sidenote: Marble Island.] [Sidenote: Prof. Tennant.] During the past season I have received from a friend a carefully labelled collection of rock-specimens from the north-west coast of Hudson’s Bay, between Eskimo Point and Chesterfield Inlet; and in connection with these a few remarks may be made on the geology of this region. Other specimens from this part of the coast were obtained in 1884 and referred to in my report for that year (page 34 D D.) My own explorations on this coast, beyond Churchill, consist of a boat voyage to a point a short distance north of Button’s Bay, in 1879, and an examination of Marble Island in 1884. The general character of the land about Chesterfield Inlet could be plainly seen from the ship when we were in that vicinity in the latter year. I have, however, received from friends who have travelled in these parts many particulars in reference to this coast. Professor James Tennant, of London, has described some rock-specimens from the north-west side of Hudson’s Bay, and also from Repulse Bay, further north. From these various sources of information some light is thrown on the geology of the coast. [Sidenote: Coast from Seal River to Eskimo Point.] [Sidenote: Probable area of limestone.]